Demosaicing method using the extended color total-variation regularization

Previously we presented a TV-based super-resolution sharpening-demosaicing method. Our previous method makes it possible to restore frequency components higher than the Nyquist frequency, and to interpolate color signals effectively while preserving their sharp color edges, without producing ringing artifacts along the edges. However, since our previous method applies the TV regularization separately to each primary color channel, as side effects it sometimes produces false color artifacts and/or zipper artifacts along sharp color edges. To remedy the drawback, in addition to the TV regularization of each primary color signal, we introduce the TV regularization of color difference signals such as G-R, and that of color sum signals such as G+R, into the TV-based super-resolution sharpening-demosaicing method. Near sharp color edges, correct interpolation provides the smallest TV norms of color difference signals or the smallest TV norms of color sum signals. Unlike our previous method, our new method jointly interpolates the three primary color channels. We compare demosaicing performance of our new method with the state-of-the-art demosaicing methods. In the evaluations, we consider a noise-free case and a noisy case. For both cases our new method achieves the best performance, and for the noisy case our new method considerably outperforms the state-of-the-art methods.